This invention relates to a method of forming tailored cast blanks, in particular from light metal alloys.
In the automotive industry many components are pressed from blanks. A blank is a piece of metal which has been cut to the right shape and is ready for pressing. More recently, a special type of blank, known as a tailored blank, has been used. A tailored blank is typically made from different thicknesses of metal and/or different grades of metal which are welded together. The main advantage of a tailored blank is that it can have different properties in different areas—for example high strength in one area and deep drawing properties and/or lower strength in another area. Tailored blanks can save weight and can also be cheaper than conventional blanks.
Another trend in the automotive industry is the increased use of aluminium alloys and other light metals such as magnesium alloys. Tailor welded blanks made from aluminium alloys have been used in the industry, but there are concerns about the integrity and performance of the welds and so the industry has been investigating other methods of producing tailored blanks which do not involve welding.
One of the methods for producing tailored blanks which does not involve welding is known as the tailor rolled blank. During the rolling process the roll gap is adjusted in a controlled manner which is synchronized with the speed of the strip so that the rolled strip has thickness changes which are synchronized with the size of the required blanks. When the blanks are then cut out of the rolled strip, they have different thicknesses in different areas.
One of the limitations of the original tailor rolled blank concept is that the thickness variations are only along the length of the rolled strip so that the thickness variation in the blank is only along one axis. In many cases this is sufficient, but for even more flexibility, the industry has also been looking at varying the thickness across the width. This is known as strip profile rolling, combining tailor rolling with strip profile rolling to simultaneously change the thickness of the strip in the longitudinal as well as in the width direction. Another area of active research is producing thickness and profile variations at the caster. For example, as described in “Twin-roll casting of strip with tailored thickness variation”. Hirt et al. Production Engineering. Research and Development (2006) Bd.13, Nr.2, S.91-94.
JP07284887 discloses casting of a thin slab and changing the width of the thin slab during casting. The cast slab can be coiled.
JP05042345 discloses casting of a strip and weirs to facilitate width change without leakage of molten steel.
From AU-A-60787/96 a strip casting method is known wherein instead of side dams, magnets are used to generate magnetic fields which are used for change of width of the casted strip. Electromagnetic fields are generating Lorentz's forces in the molten steel so that the molten metal pool can be maintained at tops of casting rolls.
JP60130450 discloses casting of a thin slab and changing the width of the thin slab during casting.
GB 2023044A discloses adjustment of cross-sectional format in continuous casting by altering the inclination of mold side walls.
DT 2550012A1 discloses a method for changing the width of a cast strand during continuous casting by means of changing the position of one mold wall during casting.
WO 2009/095264A1 disloses a method for the production of a hot-rolled TWIP-steel strip. The method is based on conventional continuous casting of a slab and direct rolling of the cast slab.
WO 2012/126697 A1 discloses metal reinforcing sheet for a B-pillar of a vehicle body consisting of a hot-formed tailor rolled blank.
Article “A review of tailored blanks—production, applications and evaluation” from the Journal of Materials Processing Technology, 214 (2014) 151-164, Merklein et al., provides an overview on tailored blanks, their production and applications e.g. in car bodies.